• Low-flow (nasal cannula, simple mask) give variable FiO2; non-rebreather masks give high FiO2.
• Venturi masks deliver a fixed, precise FiO2 - useful in COPD.
• In most acutely ill adults target SpO2 94-98%; in patients at risk of hypercapnic respiratory failure, commonly target 88-92% pending clinical assessment and blood-gas results.
• Oxygen is a drug: prescribe it and titrate to target saturations.
Memory trick
Target 94-98%, or 88-92% if at risk of hypercapnic respiratory failure.